Power shift

In 1999, against the total of 11.45 terra-watt hours (TWe) generated, nuclear power accounted for 606 MWe: 2.65 percent of the total. Year 2001 would see India produce about 2,720 MWe. The next addition of nuclear power to the power grid would only come in 2007. However, with the plant load factor up to 85 percent from 71 percent in 1998, within the NPC, there is a sense of euphoria and expectation.

The reasons are not far to seek. In a sense, criticality of RAPS-4 would mean the end of an era that spanned the long, painstaking trudge from the other reactors at Tarapore and Rajasthan. If units one and two of Tarapur are the oldest commercial boiling water reactors (BWRs) of the world, RAPS-1 and 2 are the oldest PHWRs. What’s unique about them is that they are still operating, but at de-rated capacities and with significantly less hazardous radioactive incidence on the environment and health of the manpower. Elsewhere in the world, all of them would have been scrapped.

All the pre-Narora reactors are de-rated. TAPS-1 and 2 currently operate at 160 MWe capacity, RAPS-1 and 2 at 150 and 200 MWe respectively and MAPS-1 and 2 at 170 MWe against the originally slated capacity of 220 MWe. Had they been de-commissioned – anti-nuke critics say that they should have been – apart from the huge de-commissioning costs, the nation’s power grid would have been poorer by about 1,000 MWe and it would have been a severe setback to the nuclear power industry. Indian nuclear scientists of the NPC and BARC not only prevented the de-commissioning but also innovated to sustain and continue production of power despite shutdowns due to accidents, hold-ups and a severe financial crunch.

NPC scientists proudly assert that the pre-Narora reactors are good for power production for yet another decade at the least! Chairperson and Managing Director V.K. Chaturvedi asserted that all the de-rated PHWRs would be re-rated close to their original capacities soon as refurbishing of the MAPS reactors gets underway.

RAPS station director recounts the pathetic situation the Rajasthan units faced post-Pokhran. The Canadians who supplied the units simply packed up and left. Then, RAPS-1 was not even a year old. RAPS-2 went commercial in 1981 itself, but both reactors faced one problem after another. Heavy water leaked from RAPS-1 and had to be shut down. RAPS-2 faced even more serious trouble as the coolant chambers malfunctioned. Both reactors nearly faced de-commissioning. The repairs required special technology and tools and India had nowhere to go because of the sanctions regime.

It was Dr Chaturvedi, who as project director assembled a team drawn from NPC and BARC. He plugged the leakage of heavy water in RAPS-I with tools developed on site. Then, the entire coolant channel system of RAPS-2 was replaced with indigenously developed technology.

A visit to the site revealed the scientific strides made from the trudge from RAPS-1 to RAPS-4. The later designs incorporate safety features and reduce radioactive discharges to “near zero”.

Yet, RAPS-4 would mean the end of an era in more ways than one. It could be the last 220 MWe capacity reactor to be built. Though two more such units are planned for Kaiga-3 and 4, all future PHWRs would be to the order of 500 MWe.

The demands of economies of scale have forced a temporary shift to Russian 1,000 MWe PWRs (VVERs) for Kudankulam, but the experience of the RAPS units and the success with post-Narora units have presaged a new era of nuclear power technology that exists nowhere in the world – that of Advanced Heavy Water Reactors using the closed thorium fuel cycle concept uniquely developed to exploit thorium resources in India.